Optical communications systems operating at high bit rates, such as at 10 Gb/s, 40 Gb/s or at even higher emerging bit-rates, have stringent requirements on the characteristics of the optical pulses that are communicated using such systems. Impairments to the pulse stream caused by group velocity dispersion (GVD), polarization mode dispersion (PMD), and other undesired effects can severely degrade these systems. The ability to affordably and dynamically measure these time-varying impairments, either for monitoring or compensating purposes, adds attractive functionality to a transmission network using these systems. The need for these techniques exists at the transmitter, receiver and at individual repeater locations throughout the network.